The invention relates generally to methods and systems of packaging oxygen sensitive products, and particularly to a system and method for triggering oxygen scavenging compositions for use in packaging oxygen sensitive articles.
It is well known that limiting the exposure of oxygen sensitive products to oxygen maintains and enhances the quality and shelf life of the product. For instance, by limiting the oxygen exposure of oxygen sensitive food products in the packaging system, the quality of the food product is maintained, and spoilage is reduced. In addition, such packaging also keeps the product in inventory longer, thereby reducing costs incurred from waste and having to restock.
U.S. Pat. No. 5,211,875 to Speer et al. discloses methods and compositions for scavenging oxygen. The xe2x80x9coxygen scavengingxe2x80x9d materials disclosed by Speer et al. are compositions which consume, deplete or reduce the amount of oxygen from a given environment. Oxygen scavenging materials are useful in modified atmosphere packaging and barrier packaging environments. However, the triggering of oxygen scavenging materials typically requires a relatively long time period, e.g. several minutes. xe2x80x9cTriggerxe2x80x9d and the like herein mean that process defined in U.S. Pat. No. 5,211,875, whereby oxygen scavenging is initiated by exposing a composition, film, etc. to actinic radiation having a wavelength of less than about 750 nm at an intensity of at least about 1.6 mW/cm2 or an electron beam at a dose of at least about 0.2 megarads, wherein after initiation the oxygen scavenging rate is at least about 0.05 cc oxygen per day per gram of oxidizable organic compound for at least two days after oxygen scavenging is initiated. The time consuming triggering process may adversely impact the operating speed and efficiency of the packaging system. The long exposure time associated with the triggering process may significantly heat the oxygen scavenging material and adversely impact the physical properties of the oxygen scavenging material.
It is therefore desirable to provide a method for triggering an oxygen scavenging film wherein the method uses shorter triggering steps and less overall time, whereby the method generates minimal heat; and/or which method is simple and readily incorporated into existing packaging procedures. It is also desirable to provide an apparatus for triggering an oxygen scavenging film.
In one aspect of the invention, a method for triggering an oxygen scavenging composition comprises providing an oxygen scavenging composition comprising an oxidizable organic compound; and exposing said composition to a source of pulsed light that comprises UV wavelengths wherein each pulse has a duration of between 1 microsecond and 1 millisecond, a frequency of between 0.1 and 100 Hertz, and a total intensity of at least about 350 mW/cm2; wherein each pulse provides said composition with a dose of light of at least about 0.1 J/cm2, so as to provide a triggered composition.
In a second aspect, an apparatus for triggering an oxygen scavenging composition comprises means for emitting pulses of light encompassing UV wavelengths and having a duration of between 1 microsecond and 1 millisecond and a total intensity of at least about 350 mW/cm2 so that each pulse provides a dose of light of at least about 0.1 J/cm2; and means for feeding a composition comprising an oxidizable organic compound to said means for emitting whereby said composition is exposed to pulses of said light so as to provide a triggered composition.
In a third aspect, a packaging system comprises means for emitting pulses of light encompassing UV wavelengths having a duration of between 1 microsecond and 1 millisecond and a total intensity of at least about 350 mW/cm2 so that each pulse provides a dose of light of at least about 0.1 J/cm2; means for feeding a composition having an oxidizable organic compound to said means for emitting whereby said composition is exposed to said pulses of said light so as to provide a triggered composition; means for feeding said triggered composition to a means for packaging; and means for applying said triggered composition to an article.